Conventionally, satellite communication frequency bands, an L-band, a C-band, and a Ku-band, were used to provide a wideband satellite multimedia service. Due to the restricted frequency bandwidth of the satellite communication frequency, the satellite frequency band has been replaced with a millimeter band for the satellite communication to provide a wideband multimedia service. The millimeter wave is an electromagnetic wave having a frequency in a range from about 30 to 300 GHz. That is, the millimeter wave denotes an electromagnetic wave having a millimeter wavelength.
The present invention relates to a circular polarizer having a new structure. The circular polarizer is one of major parts used for a satellite communication antenna power-feed system. The circular polarizer transforms a linear polarization to a left circular polarization or a right circular polarization.
Various conventional methods were introduced to embody a conventional circular polarizer. For example, according to a first conventional method, a circular polarizer is embodied by inserting a conductive iris structure in a rectangular or circular waveguide. According to a second conventional method, a circular polarizer is embodied by inserting conductive poles in a rectangular or circular waveguide. In a third conventional method, a circular polarizer is embodied by inserting a dielectric plate in a rectangular or circular waveguide. In a fourth conventional method, a circular polarizer is embodied by inserting a rectangular groove formed on an outer surface of a circular waveguide.
Since the conventional circular polarizers have complicated structures as described above, it is very difficult to manufacture the conventional circular polarizer for millimeter band applications. The complicated manufacturing process of the conventional circular polarizer is the major factor to increase the manufacturing cost and the testing cost. Particularly, the conventional circular polarizer having the dielectric plate has shortcomings. The conventional circular polarizer having the dielectric plate has the electric characteristic varying according to peripheral temperature characteristic, and cannot be used for dual band application.